Early Christian
tradition identified this work as a letter of John the apostle. Because of its
resemblance to the fourth gospel in style, vocabulary, and ideas, it is
generally agreed that both works are the product of the same school of
Johannine Christianity. The terminology and the presence or absence of certain
theological ideas in 1 John suggest that it was written after the gospel; it
may have been composed as a short treatise on ideas that were developed more
fully in the fourth gospel. To others, the evidence suggests that 1 John was
written after the fourth gospel as part of a debate on the proper
interpretation of that gospel. Whatever its relation to the gospel, 1 John may
be dated toward the end of the first century. Unlike 2 and 3 John, it lacks in
form the salutation and epistolary conclusion of a letter. These features, its
prologue, and its emphasis on doctrinal teaching make it more akin to a
theological treatise than to most other New Testament letters.

The purpose of the letter
is to combat certain false ideas, especially about Jesus, and to deepen the
spiritual and social awareness of the Christian community
(⇒ 1 John 3:17). Some former members
(⇒ 1 John 2:19) of the community refused to
acknowledge Jesus as the Christ (⇒ 1 John 2:22) and
denied that he was a true man (⇒ 1 John 4:2). The
specific heresy described in this letter cannot be identified exactly, but it
is a form of docetism or gnosticism; the former doctrine denied the humanity of
Christ to insure that his divinity was untainted, and the latter viewed the
appearance of Christ as a mere stepping-stone to higher knowledge of God. These
theological errors are rejected by an appeal to the reality and continuity of
the apostolic witness to Jesus. The author affirms that authentic Christian
love, ethics, and faith take place only within the historical revelation and
sacrifice of Jesus Christ. The fullness of Christian life as fellowship with
the Father must be based on true belief and result in charitable living;
knowledge of God and love for one another are inseparable, and error in one
area inevitably affects the other. Although the author recognizes that
Christian doctrine presents intangible mysteries of faith about Christ, he
insists that the concrete Christian life brings to light the deeper realities
of the gospel.

The structure and language
of the letter are straightforward yet repetitious. The author sets forth the
striking contrasts between light and darkness, Christians and the world, and
truth and error to illustrate the threats and responsibilities of Christian
life. The result is not one of theological argument but one of intense
religious conviction expressed in simple truths. The letter is of particular
value for its declaration of the humanity and divinity of Christ as an
apostolic teaching and for its development of the intrinsic connection between
Christian moral conduct and Christian doctrine.

The principal divisions of
the First Letter of John are the following: